The Republican Party is at serious risk of running out of Republican voters, according to a senior GOP lawmaker.

“Republicans need to understand that their political problems are neither tactical nor transitory,” Rep. Tom Cole (R-OK) said, as quoted by the Washington Post. “They are structural and demographic. The hard truth is the GOP coalition constitutes a shrinking portion of the electorate. To change that daunting reality, Republicans must appeal to groups that are currently outside their ranks or risk becoming a permanent minority.”

A former pollster, Cole is known to speak candidly about the political problems facing the GOP. He broke with his party late last year when he said that Republicans should accept President Barack Obama's offer to extend middle income tax cuts in the near-term. Cole also said that Republicans would be damaged politically by the recent government shutdown.